The present invention relates to a control device of a liquid crystal display device of the IPS mode or the like.
Recently, liquid crystal display devices having large substrate sizes and ones having high resolutions have come to spread. In addition, liquid crystal display devices having large viewing angles are now desired.
Among liquid crystal display devices having large viewing angles are IPS (in-plane switching)-mode liquid crystal display devices in which display is performed by driving a liquid crystal (IPS-mode liquid crystal) by lateral electric fields produced by pairs of liquid crystal driving electrodes that are provided on one substrate.
Although having large viewing angles, IPS-mode liquid crystal display devices have a problem that the response speed is low, that is, the relaxation time of liquid crystal molecule displacements corresponding to a variation of a voltage applied to a liquid crystal layer is long. More specifically, when the screen refresh rate is 60 Hz, the response time is longer than 30 ms, that is, two times or more longer than the frame period of 16.7 ms.
One method for increasing the response speed has been proposed in which the viscosity of a liquid crystal is reduced to make liquid crystal molecules to be displaced more easily by torque that is given by an electric field. More specifically, in IPS-mode liquid crystal display devices, liquid crystal molecules receive electric field torque and liquid crystal's elastic torque. Reducing the viscosity lowers the elastic torque. As a result, for the same electric field torque, the angular acceleration of liquid crystal molecules is increased by the reduction in elastic torque.
However, when the angular displacement of liquid crystal molecules is becoming small, the reduction in elastic torque makes the relaxation time longer. Since the response speed is determined by the above two factors, the method of merely reducing the viscosity of a liquid crystal cannot make the response speed sufficiently high.
In view of the above problems, it is aimed to provide a control device of a liquid crystal display device which can increase the response speed of liquid crystal display devices of the IPS mode and other modes without lowering the liquid crystal elastic torque.